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Microsoft Teams Meeting add-in interference causes Outlook Classic client failures

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Last updated
1 unique sources, 1 articles

Summary

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A known issue in Microsoft Outlook Classic renders the application unusable when the Microsoft Teams Meeting add-in is enabled. The problem stems from a previous Outlook build and affects users attempting to use Outlook Classic with the add-in active. Microsoft is actively addressing the issue and has provided temporary mitigation steps, including updating Outlook or performing an Online Repair for click-to-run installations. Additionally, Microsoft is investigating separate issues causing email connection problems in Outlook Classic, including synchronization failures with Gmail and Yahoo accounts that trigger errors 0x800CCC0F and 0x80070057.

Timeline

  1. 17.03.2026 12:37 1 articles · 2h ago

    Teams Meeting add-in causes Outlook Classic client failure due to outdated build

    Microsoft confirms that enabling the Teams Meeting add-in in Outlook Classic causes client failure due to a previous Outlook build. The company is working on a resolution and advises users to update Outlook or perform an Online Repair as temporary fixes. Microsoft is also investigating separate Outlook Classic connection issues with Gmail and Yahoo accounts that result in synchronization errors 0x800CCC0F and 0x80070057.

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Information Snippets

  • The issue occurs when the Microsoft Teams Meeting add-in is enabled in Outlook Classic.

    First reported: 17.03.2026 12:37
    1 source, 1 article
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  • The root cause is tied to a previous Outlook build version, according to Microsoft’s admin center update (EX1254044).

    First reported: 17.03.2026 12:37
    1 source, 1 article
    Show sources

  • Affected users can temporarily resolve the issue by updating Outlook or performing an Online Repair for click-to-run installations.

    First reported: 17.03.2026 12:37
    1 source, 1 article
    Show sources

  • Microsoft is also investigating Outlook Classic connection problems with Gmail and Yahoo accounts that trigger errors 0x800CCC0F and 0x80070057 during synchronization.

    First reported: 17.03.2026 12:37
    1 source, 1 article
    Show sources

  • In January 2026, Microsoft addressed another Outlook Classic issue caused by December 2025 updates that prevented opening encrypted emails for Microsoft 365 customers.

    First reported: 17.03.2026 12:37
    1 source, 1 article
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  • Microsoft mitigated a widespread Exchange Online outage (EX1253275) on March 16, 2026, affecting mailbox and calendar access via Outlook on the web, Outlook desktop, and Exchange ActiveSync.

    First reported: 17.03.2026 12:37
    1 source, 1 article
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